Becoming Beter Estimator
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Here’s a quick walkthrough of one good way to become a better estimator. The EQF (Estimating Quality Factor) Metric described in Tom DeMarco’s book Controlling Software Projects is simple to learn and gives you a meaningful score for the accuracy of your estimating history. How does it work? Pick anything you need to estimate. Let’s say we want to estimate the first day a new system is actually operational. Today, as I write, is February 11. Given what I know today, I estimate that we will go live on July 10. Now I can start my EQF histogram (Figure 1). Figure 1. Now, as time moves on, whenever I think I have a more accurate estimate than the current one, I may change my estimate. In Figure 2 we see that I have re-estimated upward twice, then lowered my estimate, then tweaked it up at the end to converge with the actual date, September 10.
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Becoming Beter Estimator
Transcript of Becoming Beter Estimator
Heres a quick walkthrough of one good way to become a better estimator
Heres a quick walkthrough of one good way to become a better estimator.
The EQF (Estimating Quality Factor) Metric described in Tom DeMarcos book Controlling Software Projects is simple to learn and gives you a meaningful score for the accuracy of your estimating history.
How does it work? Pick anything you need to estimate. Lets say we want to estimate the first day a new system is actually operational. Today, as I write, is February 11. Given what I know today, I estimate that we will go live on July 10. Now I can start my EQF histogram (Figure 1).
Figure 1.Now, as time moves on, whenever I think I have a more accurate estimate than the current one, I may change my estimate. In Figure 2 we see that I have re-estimated upward twice, then lowered my estimate, then tweaked it up at the end to converge with the actual date, September 10.
Figure 2.What would a perfect estimating history have been? Simple. You estimate September 10 from the start and never deviate. In Figure 3 that would be line AB. The area under the perfect history is rectangle ABCD.
Figure 3.Obviously, I did not have a perfect estimating history. In Figure 4 I have shaded my deviation from perfection, both under and over. Now I can score the accuracy of the estimate using the area of the perfect estimation rectangle and the area of the rectangles where I deviated from perfection.
EQF = Area of a Perfect Estimate / Area of Deviation.
Figure 4.In my example, my score is about a 5. I am averaging about 1/5 or 20 percent off.
An EQF of 5 is not too bad. The norm for schedule estimating is about a 4, with the highest sustained scores at 8 to 9. Ive never known anybody to sustain a 10 (just 10 percent off). The good news is that everybody who keeps using the EQF to assess estimates improves his or her estimating accuracy!
EQF is a great feedback mechanism you can use to improve your estimating capability. Since it applies to all kinds of estimates, you can start by just estimating your own work, and by the time you start estimating on a broader scale you will have a real feel for estimating software projectsa valuable skill in short supply in our industry.
